Biological rhythms: infradian & ultradian Flashcards
What are Infradian rhythms and examples?
- Biological rhythms with a frequency of less than one cycle in a 24 hour period e.g. menstrual cycle & seasonal affective disorder
What is the menstrual cycle?
- it is governed by monthly changes in hormone levels which regulate ovulation
- cycle refers to the first day of a women’s period to the day before her next period
- cycle takes approximately 28 days to complete
What happens during the menstrual cycle? endogenous systems
- increased oestrogen levels cause ovary to develop an egg and release it
- after ovulation increased progesterone levels help the womb lining to grow thicker- preparation for pregnancy
- if pregnancy does not occur the egg is absorbed into the body, the womb lining sheds away and leaves the body (menstrual flow)
Outline research and findings of study that shows that the menstrual cycle may be influenced by exogeneous factors
- Stern & McClintock - menstrual cycle may synchronise through influence of pheromones
- samples of pheromones gathered from p’s at different stages of menstrual cycle via a cotton pad placed in armpit (8 hours)
- pads treated with alcohol & frozen then rubbed on upper lip of other pp’s
- 68% of women experienced changes to their cycle
What is seasonal affective disorder and its symptoms?
- SAD is a depressive disorder which has a seasonal pattern of onset
- Sad is a particular type of infradian rhythm called circannual rhythm -subject to yearly cycle (winter seasons)
- main symptoms= low mood, lack of activity & interest in life
Why is SAD often referred to as the ‘winter blues’?
- symptoms are triggered during winter months, when daylight hours becomes shorter
What is the endogenous pacemaker for SAD?
endogenous pacemaker= melatonin
-during winter, lack of light in morning =secretion of melatonin longer
- has a knock on effect on production of serotonin -linked to depressive symptoms
What is a limitation of research studies menstrual cycle (Stern & McClintock)?
- study could have been subject to confounding variables
- other factors that may have influenced the women’s menstrual cycles (stress, diet, exercise)
- Also relied on women self reporting the onset & duration of their cycles
- low internal validity
What is a strength of menstrual synchrony research?
- can be explained by natural selection
- Stern and McClintock’s study > said to have some evolutionary value
- for ancestors it may have been advantageous for women to menstruate together & get pregnant at the same time
- new babies would be part of a social group who cared for one another & had access to breast milk if mother died at birth» improving their chances of survival
What are ultradian rhythms and example?
- A biological rhythm that has a cycle of more than once in a 24 hour period such as the stages of sleep
What are the stages of sleep?
- Psychologist have identified five distinct stages of sleep that span together approximately 90 minutes
- each stage is characterized by different level of brain wave activity
Describe stage 1 and 2
- Light sleep
- stage 1- brain waves have high frequency and low amplitude (alpha waves)
- stage 2 - alpha waves continue but their are random changes in patterns called spindle fibres
Describe stage 3 and 4
- deep sleep
- brain waves are delta waves with low frequency and high amplitude
Describe stage 5 (REM sleep)
- brain is paralysed
-brain produces theta waves - eyes occasionally move around (REM)
What is a strength of research into ultradian rhythms?
- improved understanding of age-related changes in sleep
- sleep scientists have observed that SWS (3 & 4) reduces with age
- Cauter et al- the resulting sleep deficit may explain various issues in old age such as reduced alertness
- To increase SWS medication may be used
